Glutathione S-transferase in humans in health and disease.

Most biological processes are catalysed by means of enzymes and study of these in health and disease is important for our understanding of both biology and disturbed function. The glutathione S-transferases (GST:E.C.2.5.1.18) are a complex multigene family of enzymes that are widely distributed in the animal kingdom. ' These enzymes possess many biological functions, the most important of which is detoxification, conjugating reduced glutathione with a large number of electrophiles.2 Such conjugation reactions result in the synthesis of mercapturic acids and represent an important excretory route for xenobiotics including carcinogens, toxins, and drugs.' As well as being concerned in the metabolism of xenobiotics, GST are involved in the metabolism of endogenous substances such as leukotriene A4 and prostaglandin A1.3 GST are also involved in non-substrate binding to such substances as bilirubin and bile acids and have an important role in hepatic anion transport. Several GST isoenzymes possess selenium-independent glutathione peroxidase activity with certain organic hydroperoxides such as linoleic and arachidonic hydroperoxide but not with hydrogen peroxide.5 In humans the cytosolic GST isoenzymes are dimeric and can be subdivided on the basis of their physicochemical and immunological properties into three major groups, namely pi, alpha, and mu class GST (Table6). In humans